A gas turbine engine generally includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section progressively increases the pressure of a working fluid entering the gas turbine engine and supplies this compressed working fluid to the combustion section. The compressed working fluid and a fuel (e.g., natural gas) mix within the combustion section and burn in a combustion chamber to generate high pressure and high temperature combustion gases. The combustion gases flow from the combustion section into the turbine section where they expand to produce work. For example, expansion of the combustion gases in the turbine section may rotate a rotor shaft connected, e.g., to a generator to produce electricity. The combustion gases then exit the gas turbine via the exhaust section.
During operation of the gas turbine, various components in the system are subjected to high temperatures. For example, high temperature combustion gases are produced in the combustion section such that various parts of the gas turbine downstream of the combustion section are subjected to high temperatures. Such parts of the gas turbine include the portion(s) of the rotor shaft that are adjacent to and downstream of the combustion section.